Field of the Invention
The present disclosure relates to a cooling system of a fuel cell vehicle, and more particularly, to a cooling system of fuel cell vehicle that actively maintains a constant heat generated in a fuel cell stack.
Description of the Related Art
An electrochemical fuel cell converts a reactant, that is, a fuel and an oxidant flow stream to generate a power and a reactant. The electrochemical fuel cell uses an electrolyte disposed between two electrodes, that is, between a cathode and an anode. Each of the electrodes includes an electrode catalyst disposed at a boundary surface between the electrolyte for inducing a desired electrochemical reaction and the electrodes. In general, the position of the electrode catalyst forms an electrochemical active range.
Generally, a polymer electrolyte membrane (PEM) fuel cell uses a membrane electrode assembly (MEA) formed of an ion-exchange membrane disposed between two electrode layers. The MEA includes a porous electrical conductive sheet material as a fluid diffusion layer such as a carbon fiber paper or a carbon cloth. In a typical MEA, the electrode layer provides a structural support for the ion-exchange membrane, and the support is, typically, thin and flexible. The membrane is ion-conductive (e.g., proton-conductive), and operates as a barrier to separate a reactant stream to one another. The membrane also operates as an electrical insulator between two electrode layers since the electrodes require electrically isolation from each other to prevent a short circuit.
The electrodes are electrically coupled to provide a path for guiding electrons between the electrodes through an external force. In the fuel cell stack, the MEA is typically disposed between two separators to which the reactant flow stream cannot penetrate physically. The separator operates as a collector and provides a support for electrode. To control the distribution to the electrochemical active range of the reactant flow stream, the surface of the separator facing the MEA may have an open-faced channel formed on the electrochemical active range. Such a channel may generally form a flow field area which corresponds to an adjacent electrochemical active range. The separator having a reactant channel formed in the electrochemical active range is known as a flow field plate.
Meanwhile, the fuel cell system includes a fuel cell stack configured to generate an electrical energy, a fuel supply system configured to supply a fuel (hydrogen) to the fuel cell stack, an air supply system configured to supply an oxygen, which is an oxidizer, in the air required for the electrochemical reaction to the fuel cell stack, and a heat and water management system configured to remove a heat of reaction of the fuel cell stack to the outside the system, and adjust an operating temperature of the fuel cell stack.
The fuel cell system having the above configuration generates electricity by an electrochemical reaction of hydrogen, which is a fuel, with oxygen in the air, and discharges a heat and water as a by-product of reaction. The fuel cell stack is a main power source of a fuel cell vehicle, and is an apparatus that produces electricity by receiving a supply of oxygen in the air and hydrogen which is fuel.
Since the fuel cell stack stably shows an optimum output effect when the cooling water adjusted to the optimum temperature is introduced into the stack, it is important to maintain the temperature of cooling water flowing into the stack at a particular temperature. Therefore, the fuel cell vehicle further includes a cooling water temperature controller in a fuel cell stack loop, configured to optimally adjust the temperature of the cooling water flowing into the stack.
Many fuel cells in the fuel cell stack are connected together in series to increase the output of an assembly. In this arrangement, one side of the plate may serve as an anode plate for one cell, and the other side may serve as a cathode plate for an adjacent cell. Additionally, the above plates may be referred to as a positive plate. However, as time is elapsed, when heat value generated in the fuel cell stack increases, and the temperature of the cooling water flowing into a bypass loop is rapidly increased, the cooling water which is cooled by being opened and closed using a proportional electromagnet is introduced to the fuel cell stack.